Tubular passage closure



Jan. 19, 1960 c. A. CRAWFORD arm. 2,921,603

TUBULAR PASSAGE CLOSURE Filed Aug. 4, 1958 INVENT R Cym/ ,4 f0

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TUBULAR PASSAGE CLOSURE Cyril A. Crawford, Donald W. McQuade, and FrankStern, Deep River, Ontario, Canada, assignors to Atomic Energy of CanadaLimited, Ottawa, Ontario, Canada, a corporation of Canada ApplicationAugust 4, 1958, Serial No. 752,691

10 Claims. (Cl. 138-89) This invention relates to scaling devices orclosures for passages in tubes and the like.

It is sometimes necessary to provide a closure for a tubular passagewhich will withstand repeated opening while maintaining its sealingeffect and which, by reason of the particular use of the passage,precludes employment of an organic sealant material. For instance, thedifficulties involved in sealing the fuel ports of a reactor pressuretube are greatly increased due to the highly radioactive field and tothe exotic materials which have to be used to limit corrosion anderosion. The effects of radiation and high temperature preclude the useof organic seals. The seal must permit repeated opening for fuelchanges. The fuel port surface against which the seal must be effectedmay be damaged by fuel handling and also may be out of round due tothermal stress effects. Generally speaking, a small leak may betolerated so long as the effect of wiredrawing to enlarge the leak canbe eliminated.

It is an object of this invention to provide a simple and effectiveclosure for a tubular passage, such closure having inorganic sealingmeans capable of repeated sealing engagement with the wall of saidpassage.

The invention will be described with reference to the accompanyingdrawing, in which Figure 1 is a sectional side elevation of a tube andclosure means in accordance with the invention, such closure being shownwith the seal open and ready for the removal of the closure, and

Figure 2 is a partial sectional side elevation of a modified form ofclosure.

In the drawing, 1 is a tube, such as a reactor pressure tube fuel port,having an internal passage 2. The closure device is generally indicatedat 3 and comprises, as shown, a hollow cylindrical body 4 having aclosed head 5 and an open end 6. A closure support 7 is threadedlymounted on the open end of body 4 by means of external thread 8 on thebody.

Any suitable means is provided for readily mounting the closure in thetube and for withdrawing the same therefrom and may comprise a breechblock mechanism including blocks 9 fixed to support 7 and insertablethrough complimentary grooves 10 in the end of the tube. In the insertedposition of the closure, the blocks 9 seat in an annular recess 11 inthe tube. A similar breech block mechanism 12 may be provided on theinterior of closure support 7 for engagement by complementary means, notshown, for withdrawal of the closure from the tube. Use of the breechblocks 9 enables the Genre support 4 to transmit a high axial force tothe tube 1, such force arising from internal pressure in the passage 2.An'ex'pansible ring 13 in closure support 7 seals against the innersurface of tube 1. A plurality of expansible rings 13a provide a sealbetween the side surface of body 4 and the interior surface of the tube1.

A rod 14 is mounted for axial movement in head 5 of body 4 and is lockedagainst rotation by means of key 2,921,608 Patented Jan. 19, 1960 15 inkeyway 16. A concave-convex disc 17 is attached to the inner end of rod14, the outer surface of the disc being concave. The disc 17 is composedof a suitable spring metallic material whereby it may be radiallyexpended in response to pressure thereon or to tension in the rod 14.and will contract to its original shape on release of pressure ortension thereon. Examples of materials from which the disc 17 may beformed are stainless steels of the types known under the trade namesType 414, Type 431, Type 440, high strength titanium alloys of the typesknown under the trade names Atlas MST6A1-4V, Republic RS-l30, RepublicRS-X, and zirconium alloys of the type known under the trade nameZircalciy. Covering the outer surface of the disc 17 is a cup 18 of asoft metal, such as gold, platinum, silver, low carbon nickel, superpure aluminum, aluminum of the type known under the trade name IS, lead,and metal of the type known under the trade name Monel. The cup has aportion 19 overlying the inner surface of disc 17 and a skirt portion 20which is spun around its underside and in close contact with the outersurface of disc 17.

The assembly of the cup 18 and the disc 17 in its original contractedform has a radius of a little less than the radius of the passage 2. Inits expanded form, the radius of the assembly tends to exceed that ofthe passage, thereby forcing a seal to be established. Means forradially expanding the assembly of the disc 17 and the cup 18 comprisesa nut 21 on the outer threaded end' of the rod 14. Clockwise rotation ofthe nut 21 causes the outer edge of the assembly of disc and cup topress axially on the closure body 4, thereby forcing the assembly toexpand radially and establish a seal. Counterclockwise rotation of thenut 21 will permit the disc 17 to contract to its original radius,thereby breaking the seal. A spring retaining ring 22 mounted in groove23 on the outermost end of the rod 14 prevents complete unsecrewing ofthe nut 21 from the rod 14, and consequent loss of the complete sealassembly in the passage 2.

The disc 17 is provided with a shoulder or hub 24 having an edge 25describing a circle around the rod 14. When tension is applied to therod 14 in order to establish a seal, the edge 25 is caused to come intocontact with the surface of a conical recess 26 in closure body 4. Thiscauses a secondary seal to be established preventing leakage through theannular gap between the rod 14 and the closure body 4 and through thekeyway 16. Such leakage could occur if the cup 18 and the disc 17 wereto fail by rupture or erosion. To prevent expansion of liquid trappedbetween the disc 17 and the closure body 4 from exerting excess pressureon the outer surface of the disc 17 and thereby causing the seal tobreak, a passage 27 can be provided in the closure body extending fromrecess 26 to the annulus between the side surface of body 4 and the tubeand allowing such liquid to drain into this low pressure annulus betweenthe closure body and the tube 1.

Should a leak occur between the cup 18 and the inner surface of the tube1, the pressure in the annulus between the closure body 4 and the tube 1will increase greatly due to the sealing action of the piston rings 13ain the closure body 4. The pressure difference established across theleak path will therefore be greatly reduced, and the effect ofwiredrawing which would tend to erode the leak path rapidly will beslowed down or eliminated. The expansible n'ngs 13a are so arrangedthat, as far as possible, the total pressure drop will be dividedequally between them. This will be achieved by means of orifices 28 insome or all of these rings. The ring 13 in the closure support 7 willnot have any orifices and will tend to establish a secondary seal. Thiswill cause a rise of pressure in a monitoring tube 29 which may beprovided in tube 1 to detect and identify the leaky closure. Such meansof remote leak detection will be necessary in a reactor since it willhave about five hundred of these closures, and the radioactive field intheir region makes direct observation impractical.

In some instances, the sealing surface in the tube 1 will become damagedby wiredrawing due to such a leak. Thus, it may be desirable to providea new closure sealing in a different position in the tube. This mayreadily be accomplished by providing a plurality of spacer rings 30between the closure body 4 and support 7. By varying the number of suchspacers, the new closure is enabled to seal upon an undamaged surface inthe passage 2.

In the modified form of the invention illustrated in Figure 2, the softmetal cup 18 has been eliminated and replaced by a soft surface layer 31in the peripheral region 32 of the disc 17. This layer 31 may comprise aplate of soft metal such as gold plated directly onto the disc 17.Alternatively, the region 32 of the disc 17 may be subjected to adifierential metallurgical treatment to soften the material of the discin such region.

The nut 21, the key 15, keyway 16 and the threaded portion on the rod 14have been eliminated, and replaced by a spring retaining ring 33 on theend of the rod 14. This ring is situated so as to maintain the rod 14under slight tension when the disc 17 is contracted. A seal isestablished by increasing the pressure in the passage 2, which willexert an axial force on the disc 17 causing it to expand radially andestablish a seal. The passage 27 is taken behind at least one pistonring in this case in order to establish a difference of prmsure acrossthe disc 17. This passage 27 may be so arranged that the seal contractscompletely if a leak occurs. All damage to the sealing surface in thepassage 2 will therefore be prevented. Temporary sealing action will beprovided by the piston rings. An alternative means of providing orificespast the piston rings is also shown in Figure 2. This means comprises apassage 34 drilled in the closure body 4, and small orifice holes 35,drilled radially in the lands between piston rings, to join the axialpassage 34.

We claim:

1. A closure for a tubular passage comprising a cylindrical closure bodyarranged for insertion in said passage and adapted to provide an annularspace between said body and the wall of said passage, a plurality ofexpansible rings carried by said body and adapted to engage said passagewall to seal said annular space, said body having a head, a rod axiallymounted in said head. for

reciprocal movement therein, a concavo-convex radially expansible springmetal disc fixed to one end of said M, a soft metal sealing elementcarried by said disc ind overlying the periphery thereof, the peripheralporspace, said body having a head, a rod axially mounted in said head,and a concave-convex radially expansible spring metal disc fixed to oneend of said rod, a soft metal sealing element carried by said disc andoverlying the periphery thereof, the peripheral portion of said discbearing upon said head, said disc and sealing element being radiallyexpansible in response to pressure thereon against said head.

3. A closure as defined in claim 2, said soft metal element comprising acup-shaped member extending over the forward face of said disc and theperipheral portion thereof.

4. A closure as defined in claim 2, said soft metal element comprising alayer of soft metal bonded to the peripheral portion of said disc.

5. A closure as defined in claim 2, including secondary sealing meanscomprising an annular shoulder on said disc adjoining its juncture withsaid rod, said body having a wall defining a conical recess surroundingsaid shoulder, said shoulder in response to expansive movement of saiddisc being engageable with said recess wall.

6. A closure as defined in claim 5, said body having a passage leadingfrom said recess to said annular space.

7. A closure as defined in claim 2, including a support for said body,and means for mounting said support and body in said tube fornon-reciprocal movement there- 8. A closure as defined in claim 7,including a plurality of spacers between said support and said body,said spacers being individually movable to vary the longitudinalrelation of said body with respect to said support.

9. A closure as defined in claim 2, certain of said expansible ringshaving orifices therein.

10. A closure as defined in claim 2, said body having a passage thereinbypassing said expansible rings.

References Cited in the file of this patent UNITED STATES PATENTS1,393,316 Roth Oct. 11, 1921 2,139,491 Dawson Dec. 6, 1938

